The present invention relates to chains, and in particular to a sealed bushing design used in a chain assembly.
In chains used in ditching machines, earth scraping machines and in similar applications involving operation in abrasive environments, it has been desirable to protect the chain bushings by keeping the bushing and/or pin lubricated and by preventing abrasive material from entering the bushing or pin surfaces. Historically, this has been accomplished by sealing the chain joint or the space between the adjoining plates of interconnected links. There exists in the prior art a plethora of expedients teaching the use of seals between inner and outer sidebars of chain assemblies. Typical of these teachings are the seals disclosed in the current assignee's previous U.S. Pat. Nos. 3,135,128 to Rudolph and 4,464,151 to Kahl which focus on the specific construction of seals used in the chain joint.
Solutions of the problems as set forth by the prior art discussed above have not been readily transferable to related problems confronting those skilled in the art of manufacturing and using chain. In the present situation, it is desirable to fabricate a chain using a stud bushing which would function under heavy loads in hostile environments. For example, a tramming chain used in shuttle cars for underground coal mining is frequently subjected to sulfuric acid in mine water which eats away and corrodes the bushing. Especially destructive in this design is the proclivity of corrosive material or liquid to work down into the crevice between the innermost surface of the inner sidebars and the outside diameter of the bushing where the material or liquid attacks the reduced diameter of the stud bushing. In similar chains, using rollers over the bushings or bushings which are sunk into the inner sidebar portions, the problem is still extant. Further, lubricant applied during assembly or maintenance of the chain tends to escape from between the bushing outside diameter and the inner sidebars.
While the known prior art was busy improving upon the shape and arrangement of seals between the inner and outer sidebars, it did not recognize the problem of fatigue originating at the critically stressed bushing surface interfacing with the innermost surface of the inner sidebars. Some attempts have been made to lessen the chain fatigue by increasing the thickness of the inner sidebar so as to alter the geometry of the chain parts and make the bushing fit better but these have not been totally successful and add to the additional weight and cost of the chain. It was with these constraints in mind that the applicant sought to provide a chain which would stand high loads and operate in environments in which most chain would deteriorate due to attack on the exposed bushing surface on the innermost side of the inner sidebars of the chain.
Accordingly, it is a principal object of the invention to provide a sealed bushing design for a chain assembly which is protective against corrosive materials.
Another object of the invention is the provision of a seal which adds lubricant to a critical bearing surface and retains the lubricant on the bearing surface.
Another object of the invention is to furnish a simple seal strategically placed on the bushing at the inner sidebar of a chain assembly so as to prevent fatigue of the bushing and extend the life of the chain.
A further object of the invention is to provide a seal for a chain link assembly employing a stud bushing for heavy mining and other applications.